VARIATIONS OF TEMPERATURE 339 



and between 3 and 4 in the afternoon it is at its highest. This 

 rhythm or periodicity is shown by night workers as well as by 

 those who live a normal average life. Benedict tells of a night 



FIG. 72. Chart of the Daily Variation of Temperature in the Normal Human Subject, 

 in degrees Centigrade. The hours are marked from midnight. (Richet.) 



watchman who for seven years had been working during the night 

 and sleeping during the clay, and had his maximum temperature 

 about 4 o'clock in the afternoon when sound asleep and his 

 minimum about 4 o'clock in the morning when he was awake and 

 active. 



It is common knowledge that certain means may be taken to bring 

 about alterations in the body temperature : 



1. Muscular exercise causes heat. 



2. Want of muscular exercise is followed by cooling, e.g. cold has to be 

 guarded against during sleep. 



3. Heat or work causes sweating. 



4. Heat produces lassitude. Compare the day's work of a man in 

 Spain with that of a man in Scotland. 



5. Still air has the same effect as that of heat on the feeling of lassitude. 

 The production of a movement of the air removes the tired feeling. 



6. A higher temperature can be endured in a Turkish than in a plunge 

 bath. Further, a hot dry climate is comfortably endured, while air at 

 the same temperature, but saturated with moisture, oppresses. 



7. Cold air does not chill one to the same extent as water at the same 

 temperature. Cold much more severe than is experienced in Britain may 

 be enjoyed in the dry, Canadian climate. 



For example, a temperature of - 40 may be borne if the air be dry and 

 still, while a much warmer but damp and windy atmosphere may " cut 

 to the bone." 



8. Ingestion of hot or cold food or of heat-producing food normally 

 produces an almost negligible increase in rectal temperature. 



